Magnetic media or magnetic stripes on credit, identification, or debit cards are widely used for identification and authorization of financial transactions. The data recorded follows established ANSI or ISO/IEC standards. However, these established uses of magnetic stripes on credit cards is prone to fraud, since the code is readable through a card reader or other methods and can be easily duplicated. The prior art discloses cards and card systems that include a processor and associated electronics to make a credit, identification, or debit card programmable and readable in the existing installed base of card readers. However, such prior art card systems use power inefficiently. Thus there is a need for a card and a method for processing the data stored in the card that uses power more efficiently than does card systems of the prior art.